The present invention relates to a tube joint and a method for forming a tube joint, and in particular to a joint formed with adhesives and a metal forming process.
Numerous methods of joining tubes together have been developed. Many of these methods rely on welding two tubes together in a butt joint. Such a joint works well when the two tubes joined together are of the same material. However, when tubes of different materials am being joined, it is difficult or impossible to form a strong joint by welding. Tube joints with dissimilar materials are often formed using an adhesive compound such as an epoxy resin which is adhesive to both materials. However, an adhesive joint does not always provide the strength necessary when the tubes are being joined together to form a structural system or frame, such as a frame for a seat assembly.
Accordingly, it is an object of the present invention to provide a tube joint and a method for forming the joint which can be used equally well with like materials or dissimilar materials to provide the necessary strength for a structural frame.
The joint of the present invention is formed by first producing a flare at one end of an outer tube. An inner tube is placed within the outer tube, beyond the flare, forming a telescoped portion in which the outer tube overlaps the inner tube, adjacent to the flare. The flare forms a clearance between the inner and outer tubes at the end of the outer tube. An adhesive is disposed in this clearance by placing an annular bead of adhesive around the inner tube prior to inserting the inner tube into the outer tube.
A metal forming process is performed on the tubes at the location of the overlapping inner and outer tubes, producing apertures extending radially through both tubes. The aperture in the inner tube is concentric with the aperture in the outer tube. The aperture in the outer tube is surrounded by a radially inwardly directed flange which extends into the aperture in the inner tube. This flange mechanically interlocks the inner and outer tubes together. The forming process can be performed by a punch, a flow-drill or a similar tool. Several circumferentially spaced sets of apertures can be formed in the tube joint.
The joint thus formed has several advantages. The joint can be used with dissimilar materials or like materials with equal results. In addition, the joint quality is more consistent and the joint is lower in cost than a welded joint.
Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings.